HDFS-13653. Make dfs.client.failover.random.order a per nameservice configuration. Contributed by Ekanth Sethuramalingam.

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/ConfiguredFailoverProxyProvider.java

@@ -94,9 +94,7 @@ public ConfiguredFailoverProxyProvider(Configuration conf, URI uri,
         proxies.add(new AddressRpcProxyPair<T>(address));
       }
       // Randomize the list to prevent all clients pointing to the same one
-      boolean randomized = conf.getBoolean(
-          HdfsClientConfigKeys.Failover.RANDOM_ORDER,
-          HdfsClientConfigKeys.Failover.RANDOM_ORDER_DEFAULT);
+      boolean randomized = getRandomOrder(conf, uri);
       if (randomized) {
         Collections.shuffle(proxies);
       }
@@ -111,6 +109,31 @@ public ConfiguredFailoverProxyProvider(Configuration conf, URI uri,
     }
   }
 
+  /**
+   * Check whether random order is configured for failover proxy provider
+   * for the namenode/nameservice.
+   *
+   * @param conf Configuration
+   * @param nameNodeUri The URI of namenode/nameservice
+   * @return random order configuration
+   */
+  private static boolean getRandomOrder(
+      Configuration conf, URI nameNodeUri) {
+    String host = nameNodeUri.getHost();
+    String configKeyWithHost = HdfsClientConfigKeys.Failover.RANDOM_ORDER
+        + "." + host;
+
+    if (conf.get(configKeyWithHost) != null) {
+      return conf.getBoolean(
+          configKeyWithHost,
+          HdfsClientConfigKeys.Failover.RANDOM_ORDER_DEFAULT);
+    }
+
+    return conf.getBoolean(
+        HdfsClientConfigKeys.Failover.RANDOM_ORDER,
+        HdfsClientConfigKeys.Failover.RANDOM_ORDER_DEFAULT);
+  }
+
   @Override
   public Class<T> getInterface() {
     return xface;

hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestConfiguredFailoverProxyProvider.java

@@ -0,0 +1,264 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode.ha;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
+import org.apache.hadoop.hdfs.protocol.ClientProtocol;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.test.GenericTestUtils;
+import org.apache.hadoop.util.Time;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.mockito.invocation.InvocationOnMock;
+import org.mockito.stubbing.Answer;
+import org.slf4j.event.Level;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Test {@link ConfiguredFailoverProxyProvider}.
+ * This manages failover logic for a given set of nameservices/namenodes
+ * (aka proxies).
+ */
+public class TestConfiguredFailoverProxyProvider {
+  private Configuration conf;
+  private int rpcPort = 8020;
+  private URI ns1Uri;
+  private URI ns2Uri;
+  private String ns1;
+  private String ns1nn1Hostname = "machine1.foo.bar";
+  private InetSocketAddress ns1nn1 =
+      new InetSocketAddress(ns1nn1Hostname, rpcPort);
+  private String ns1nn2Hostname = "machine2.foo.bar";
+  private InetSocketAddress ns1nn2 =
+      new InetSocketAddress(ns1nn2Hostname, rpcPort);
+  private String ns2;
+  private String ns2nn1Hostname = "router1.foo.bar";
+  private InetSocketAddress ns2nn1 =
+      new InetSocketAddress(ns2nn1Hostname, rpcPort);
+  private String ns2nn2Hostname = "router2.foo.bar";
+  private InetSocketAddress ns2nn2 =
+      new InetSocketAddress(ns2nn2Hostname, rpcPort);
+  private String ns2nn3Hostname = "router3.foo.bar";
+  private InetSocketAddress ns2nn3 =
+      new InetSocketAddress(ns2nn3Hostname, rpcPort);
+  private static final int NUM_ITERATIONS = 50;
+
+  @BeforeClass
+  public static void setupClass() throws Exception {
+    GenericTestUtils.setLogLevel(RequestHedgingProxyProvider.LOG, Level.TRACE);
+  }
+
+  @Before
+  public void setup() throws URISyntaxException {
+    ns1 = "mycluster-1-" + Time.monotonicNow();
+    ns1Uri = new URI("hdfs://" + ns1);
+    conf = new Configuration();
+    conf.set(
+        HdfsClientConfigKeys.DFS_HA_NAMENODES_KEY_PREFIX + "." + ns1,
+        "nn1,nn2,nn3");
+    conf.set(
+        HdfsClientConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY + "." + ns1 + ".nn1",
+        ns1nn1Hostname + ":" + rpcPort);
+    conf.set(
+        HdfsClientConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY + "." + ns1 + ".nn2",
+        ns1nn2Hostname + ":" + rpcPort);
+    conf.set(
+        HdfsClientConfigKeys.Failover.PROXY_PROVIDER_KEY_PREFIX + "." + ns1,
+        ConfiguredFailoverProxyProvider.class.getName());
+    conf.setBoolean(
+        HdfsClientConfigKeys.Failover.RANDOM_ORDER + "." + ns1,
+        false);
+
+    ns2 = "myroutercluster-2-" + Time.monotonicNow();
+    ns2Uri = new URI("hdfs://" + ns2);
+    conf.set(
+        HdfsClientConfigKeys.DFS_HA_NAMENODES_KEY_PREFIX + "." + ns2,
+        "nn1,nn2,nn3");
+    conf.set(
+        HdfsClientConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY + "." + ns2 + ".nn1",
+        ns2nn1Hostname + ":" + rpcPort);
+    conf.set(
+        HdfsClientConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY + "." + ns2 + ".nn2",
+        ns2nn2Hostname + ":" + rpcPort);
+    conf.set(
+        HdfsClientConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY + "." + ns2 + ".nn3",
+        ns2nn3Hostname + ":" + rpcPort);
+    conf.set(
+        HdfsClientConfigKeys.Failover.PROXY_PROVIDER_KEY_PREFIX + "." + ns2,
+        ConfiguredFailoverProxyProvider.class.getName());
+    conf.setBoolean(
+        HdfsClientConfigKeys.Failover.RANDOM_ORDER + "." + ns2,
+        true);
+
+    conf.set(HdfsClientConfigKeys.DFS_NAMESERVICES, ns1 + "," + ns2);
+    conf.set("fs.defaultFS", "hdfs://" + ns1);
+  }
+
+  /**
+   * Tests getProxy with random.order configuration set to false.
+   * This expects the proxy order to be consistent every time a new
+   * ConfiguredFailoverProxyProvider is created.
+   */
+  @Test
+  public void testNonRandomGetProxy() throws Exception {
+    final AtomicInteger nn1Count = new AtomicInteger(0);
+    final AtomicInteger nn2Count = new AtomicInteger(0);
+
+    Map<InetSocketAddress, ClientProtocol> proxyMap = new HashMap<>();
+
+    final ClientProtocol nn1Mock = mock(ClientProtocol.class);
+    when(nn1Mock.getStats()).thenAnswer(createAnswer(nn1Count, 1));
+    proxyMap.put(ns1nn1, nn1Mock);
+
+    final ClientProtocol nn2Mock = mock(ClientProtocol.class);
+    when(nn2Mock.getStats()).thenAnswer(createAnswer(nn2Count, 2));
+    proxyMap.put(ns1nn2, nn2Mock);
+
+    ConfiguredFailoverProxyProvider<ClientProtocol> provider1 =
+        new ConfiguredFailoverProxyProvider<>(conf, ns1Uri,
+            ClientProtocol.class, createFactory(proxyMap));
+    ClientProtocol proxy1 = provider1.getProxy().proxy;
+    proxy1.getStats();
+    assertEquals(1, nn1Count.get());
+    assertEquals(0, nn2Count.get());
+    proxy1.getStats();
+    assertEquals(2, nn1Count.get());
+    assertEquals(0, nn2Count.get());
+    nn1Count.set(0);
+    nn2Count.set(0);
+
+    for (int i = 0; i < NUM_ITERATIONS; i++) {
+      ConfiguredFailoverProxyProvider<ClientProtocol> provider2 =
+          new ConfiguredFailoverProxyProvider<>(conf, ns1Uri,
+              ClientProtocol.class, createFactory(proxyMap));
+      ClientProtocol proxy2 = provider2.getProxy().proxy;
+      proxy2.getStats();
+    }
+    assertEquals(NUM_ITERATIONS, nn1Count.get());
+    assertEquals(0, nn2Count.get());
+  }
+
+  /**
+   * Tests getProxy with random.order configuration set to true.
+   * This expects the proxy order to be random every time a new
+   * ConfiguredFailoverProxyProvider is created.
+   */
+  @Test
+  public void testRandomGetProxy() throws Exception {
+    final AtomicInteger nn1Count = new AtomicInteger(0);
+    final AtomicInteger nn2Count = new AtomicInteger(0);
+    final AtomicInteger nn3Count = new AtomicInteger(0);
+
+    Map<InetSocketAddress, ClientProtocol> proxyMap = new HashMap<>();
+
+    final ClientProtocol nn1Mock = mock(ClientProtocol.class);
+    when(nn1Mock.getStats()).thenAnswer(createAnswer(nn1Count, 1));
+    proxyMap.put(ns2nn1, nn1Mock);
+
+    final ClientProtocol nn2Mock = mock(ClientProtocol.class);
+    when(nn2Mock.getStats()).thenAnswer(createAnswer(nn2Count, 2));
+    proxyMap.put(ns2nn2, nn2Mock);
+
+    final ClientProtocol nn3Mock = mock(ClientProtocol.class);
+    when(nn3Mock.getStats()).thenAnswer(createAnswer(nn3Count, 3));
+    proxyMap.put(ns2nn3, nn3Mock);
+
+
+    for (int i = 0; i < NUM_ITERATIONS; i++) {
+      ConfiguredFailoverProxyProvider<ClientProtocol> provider =
+          new ConfiguredFailoverProxyProvider<>(conf, ns2Uri,
+              ClientProtocol.class, createFactory(proxyMap));
+      ClientProtocol proxy = provider.getProxy().proxy;
+      proxy.getStats();
+    }
+
+    assertTrue(nn1Count.get() < NUM_ITERATIONS && nn1Count.get() > 0);
+    assertTrue(nn2Count.get() < NUM_ITERATIONS && nn2Count.get() > 0);
+    assertTrue(nn3Count.get() < NUM_ITERATIONS && nn3Count.get() > 0);
+    assertEquals(NUM_ITERATIONS,
+        nn1Count.get() + nn2Count.get() + nn3Count.get());
+  }
+
+  /**
+   * createAnswer creates an Answer for using with the ClientProtocol mocks.
+   * @param counter counter to increment
+   * @param retVal return value from answer
+   * @return
+   */
+  private Answer<long[]> createAnswer(final AtomicInteger counter,
+      final long retVal) {
+    return new Answer<long[]>() {
+      @Override
+      public long[] answer(InvocationOnMock invocation) throws Throwable {
+        counter.incrementAndGet();
+        return new long[]{retVal};
+      }
+    };
+  }
+
+  /**
+   * createFactory returns a HAProxyFactory for tests.
+   * This uses a map of name node address to ClientProtocol to route calls to
+   * different ClientProtocol objects. The tests could create ClientProtocol
+   * mocks and create name node mappings to use with
+   * ConfiguredFailoverProxyProvider.
+   */
+  private HAProxyFactory<ClientProtocol> createFactory(
+      final Map<InetSocketAddress, ClientProtocol> proxies) {
+    final Map<InetSocketAddress, ClientProtocol> proxyMap = proxies;
+    return new HAProxyFactory<ClientProtocol>() {
+      @Override
+      public ClientProtocol createProxy(Configuration cfg,
+          InetSocketAddress nnAddr, Class<ClientProtocol> xface,
+          UserGroupInformation ugi, boolean withRetries,
+          AtomicBoolean fallbackToSimpleAuth) throws IOException {
+        if (proxyMap.containsKey(nnAddr)) {
+          return proxyMap.get(nnAddr);
+        } else {
+          throw new IOException("Name node address not found");
+        }
+      }
+
+      @Override
+      public ClientProtocol createProxy(Configuration cfg,
+          InetSocketAddress nnAddr, Class<ClientProtocol> xface,
+          UserGroupInformation ugi, boolean withRetries) throws IOException {
+        if (proxyMap.containsKey(nnAddr)) {
+          return proxyMap.get(nnAddr);
+        } else {
+          throw new IOException("Name node address not found");
+        }
+      }
+    };
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -3634,6 +3634,18 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.client.failover.random.order</name>
+  <value>false</value>
+  <description>
+    Determines if the failover proxies are picked in random order instead of the
+    configured order. The prefix can be used with an optional nameservice ID
+    (of form dfs.client.failover.random.order[.nameservice]) in case multiple
+    nameservices exist and random order should be enabled for specific
+    nameservices.
+  </description>
+</property>
+
 <property>
   <name>dfs.client.key.provider.cache.expiry</name>
   <value>864000000</value>

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/tools/TestHdfsConfigFields.java

@@ -41,6 +41,7 @@ public class TestHdfsConfigFields extends TestConfigurationFieldsBase {
   public void initializeMemberVariables() {
     xmlFilename = new String("hdfs-default.xml");
     configurationClasses = new Class[] { HdfsClientConfigKeys.class,
+        HdfsClientConfigKeys.Failover.class,
         HdfsClientConfigKeys.StripedRead.class, DFSConfigKeys.class,
         HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.class };